The present invention is directed to improvements in a supercharging system for starting internal combustion engines which improves the structure and efficiency of systems heretofore used.
In previous internal combustion engines the concern of manufacturers and designers has been to increase the power of the engines. Among the techniques used, the most important is that of supercharging. Supercharging consists of charging a reciprocating internal combustion engine with an increased fuel-air mixture which is greater in quantity than that which can be conventionally suctioned by the engine alone. This supercharging generally can be accomplished by means of compressors which can be driven directly by the engine, with a mechanical coupling, or else by means of a turbine which is activated by the exhaust gases. The power which is obtained from a supercharged engine is considerably higher than that of an engine having a like cylinder capacity which has not been supercharged. The compressors used can be of various types such as volumetric, blade, centrifugal, etc. and having rotational speeds which can reach extremely high levels such as those in the most modern centrifugal type devices. Superchargers are particularly important when applied to aeronautic engines wherein they perform the dual functions of improving the weight/power ratio and reducing losses in power due to decreased atmospheric pressure corresponding to the height at which an airplane travels. Another important use of superchargers is in diesel engines as well as in racing cars.
In spite of the above-described advantages, supercharging of internal combustion engines has been restricted due to the fact that the internal pressure during ignition increases simultaneously as well as the corresponding mechanical and thermal loads on the pistons and support bearings of the various movable parts. To prevent this effect, the supercharging must be accompanied by a correlative reduction in the compression ratio of the engine. This reduction does not pose any problems when the engine is in full operation, since the yield of the compression ratios of the engine and the turbocharger will give the same result as a conventional non-supercharged engine. This reduction in compression ratio of the engine does however, pose serious problems when starting said engines.
In fact, during ignition, the turbocharger which supercharges the engine is inoperative and thus, only the compression ratio of the engine itself can be counted on to start the engine. The engine compression is insufficient by itself to reach the temperature necessary for the ignition of the fuel and the result is that the engine cannot be started.